Velocity and acceleration are both vectors; they have a direction. What is thedirection of the velocity and acceleration vectors
1 answer:
Answer:
d. Both A & C
Explanation:
- The velocity of the ball is a vector, whose magnitude indicates its rate of change of position, and it has a direction. In this case, the ball is moving upward, therefore the direction of motion is upward, so the direction of the velocity is upward as well.
- The acceleration of the ball is a vector, whose magnitude indicates the rate of change of the velocity. The direction of the acceleration is:
-- positive if the the magnitude of the velocity is increasing
-- negative if the magnitude of the velocity is decreasing
For a ball thrown upward, the acceleration is given by the acceleration of gravity, . This acceleration points downward, and it is constant during the entire motion. In particular, it does not change direction, as it is always directed downward. Therefore, the acceleration of the ball is downward.
So, the correct answer is
d.Both A & C
Since A and C are both true:
a.The velocity vector is directed upward.
c.The acceleration is directed downward.
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Answer:
Part a) Force on car = 2833.84 Newtons
Part b) Time to stop the car = 3.8 seconds
Part c) Factor for stopping distance is 4.
Part d) Factor for stopping time is 1.
Explanation:
The deceleration produced when the car is brought to rest in 20 meters can be found by third equation of kinematics as
where
v = final speed of the car ( = 0 in our case since the car stops)
u = initial speed of the car = 38 km/hr =
a = deceleration produces
s = distance in which the car stops
Applying the given values we get
Now the force can be obtained using newton's second law as
Applying values we get
The negative direction indicates that the force is opposite to the motion of the object.
Part b)
The time required to stop the car can be found using the first equation of kinematics as
with symbols having the same meanings
Applying values we get
Part c)
From the developed relation of stopping distance we can see that the for same force( Same acceleration) the stopping distance is proportional to the square of the initial speed thus doubling the initial speed increases the stopping distance 4 times.
Part d)
From the relation of stopping time and the initial speed we can see that the stopping distance is proportional initial speed thus if we double the initial speed the stopping time also doubles.